1. Field of the Invention
This invention generally relates to a device for fastening a flywheel, to the output end of the crankshaft of an internal combustion engine, the flywheel being combined into a single component with a clutch pressure plate unit and a clutch disc.
2. Background Information
Conventional friction clutches of motor vehicles generally can have a one-piece or two-piece flywheel, on which a pressure plate unit can be fastened, usually in a detachable manner, by means of bolts or screws. The pressure plate unit can have an axially movable contact plate which can be guided in a non-rotating, but axially movable, manner on a clutch housing boiled to the flywheel. A prestress can be applied to the pressure plate unit preferably by a clutch main spring, which main spring can typically be a membrane spring, thereby biasing the pressure plate preferably towards the flywheel. The application plate or pressure plate and the flywheel can form friction surfaces for a clutch disc located between them, the hub of which clutch disc can be sealed so that it essentially does not rotate but can move axially on an input shaft of a transmission. The input shaft of a transmission is typically downstream in the drive train of the motor vehicle. On the other side of the flywheel, the flywheel can be bolted to an end flange of the crankshaft of the internal combustion engine by means of a number of bolts located around the axis of rotation of the crankshaft.
On conventional friction clutches, the clutch disc and the membrane spring, viewed in the axial direction, can cover the bolts which can hold the flywheel to the end flange of the crankshaft. During the assembly of the friction clutch, therefore, the flywheel typically must first be bolted to the end flange of the crankshaft, before the clutch disc can be installed, and then the pressure plate unit can be bolted to the flywheel. This assembly process is not only time-consuming, but also can have the disadvantage that the friction clutch as a whole cannot be inspected before assembly, i.e. when it includes the clutch disc and the flywheel, to make certain that the clutch unit complies with specifications.
DE-A-41 17 571 discloses both a clutch disc and a membrane spring with holes which are axially aligned with the bolts on the end flange of the crankshaft for fastening the flywheel. In this manner, the pressure plate unit can be assembled with the clutch disc and the flywheel preferably into a single component (modular clutch), even before they are mounted on the crankshaft. The fastening bolts can then preferably be tightened through the holes in the clutch disc and the membrane spring into the end flange of the crankshaft.
DE-A-33 15 232 teaches that a modular clutch consisting of a flywheel, pressure plate unit and clutch disc, on which the clutch housing can be crimped around the flywheel, i.e. the clutch housing is preferably not detachably connected to the flywheel, can be bolted by means of a central bolt onto the output end of the crankshaft. The output end of the crankshaft can have a centric end opening preferably with an internal thread, into which the internal central bolt is bolted. The central bolt can have a radially-projecting flange which can brace the flywheel against the axial end surface of the output end of the crankshaft. The central bolt can be designed as a hollow bolt and also can have a pilot bearing. The pilot bearing can radially guide the engine-side end of the transmission input shaft, which input shaft can extend through the hub of the clutch disc. The torque which can be transmitted via the radial flange of the central bolt, however, can be comparatively low, since only limited starting torques can be achieved for the central bolt.
To fasten the flywheel, DE-A-40 13 298 discloses a modular clutch which can have the facing axial surfaces of an end flange of the crankshaft and of the flywheel equipped with radial gear teeth, (e.g. serration). The flywheel can, in turn, be axially fixed to the output end of the crankshaft by means of a central bolt, which central bolt also contains the pilot bearing of the transmission input shaft. In this case, the central bolt performs essentially the axial fixing function only, while the torque can be transmitted from the crankshaft to the flywheel by means of the radial gear teeth.. The central bolt which can be screwed into a threaded central opening on the output end of the crankshaft can have key slots in the vicinity of the pilot bearing. A screwdriver can be inserted into the key slots through the hub of the clutch disc, to tighten the central bolt to the crankshaft.
Finally, in the book entitled "Die Motoren der Personenkraftwagen" ["The Engines of Passenger Cars"], by K. Wiecking and R. Gebauer, Verlag Chr. Belser, Stuttgart, 1952, Page 314, FIG. 341, it is disclosed that the flywheel of a conventional friction clutch can be fastened to the output end of the crankshaft of the internal combustion engine, by means of a cone-interference fit connection. The output end has an external cone which can taper toward the clutch disc, onto which clutch disc the flywheel can be placed, by means of an internal cone on the hub of the flywheel. The output end of the crankshaft can end in a threaded pin, onto which threaded pin a nut which can secure the flywheel can be screwed. However, the design of the known arrangements does not make it possible to install the pressure plate unit with the clutch disc and the flywheel as a single component.